Temperature regulation in burying beetles (Nicrophorusspp.:Coleoptera: Silphidae): effects of body size, morphology and environmental temperature

Abstract

This study compares the thermoregulatory ability of three species of burying beetle (Coleoptera: Silphidae: Nicrophorus hybridus, Nicrophorus guttula and Nicrophorus investigator) that vary significantly in body size. It also explores possible mechanisms for temperature regulation in burying beetles, including physiological and behavioral thermoregulatory strategies, and the influence of environmental temperatures on body temperature and activity times. We measured beetle thoracic and abdominal temperatures before and after short (<5·s) flights, and thoracic temperature during sustained, tethered flights and following flight in the field. We calculated two measures of thermoregulatory ability: the slope of post-flight thoracic temperature against ambient air temperature and the slope of post-flight thoracic temperature against operative flight temperature. Thoracic temperatures following flight were significantly higher than abdominal temperatures, and the largest species, N. hybridus, was determined to be the better thermoregulator, with regression slopes closer to zero (0.315-0.370) than N. guttula (0.636-0.771) or N. investigator (0.575-0.610). We also examined the roles that insulation, wing loading, physiological heat transfer, basking and perceived environmental temperature play on temperature regulation and activity times in Nicrophorus. This study shows that body size, morphological features, such as wing loading and insulation, and perceived environmental temperatures affect thermoregulation and activity times in burying beetles.

Endothermy of dynastine scarab beetles (Cyclocephala colasi)associated with pollination biology of a thermogenic arum lily(Philodendron solimoesense)

“…It could be argued that endothermy at cooler temperatures was related to attempts to escape. There is no question that endothermy is associated with preparation for flight in beetles (Bartholomew and Casey, 1977a;Bartholomew and Casey, 1977b;Bartholomew and Heinrich, 1978;Chown and Scholtz, 1993;Merrick and Smith, 2004;Oertli, 1989). When averaged data from 24-h experiments are associated with time of day, there was a clear circadian rhythm in endothermy, despite all measurements being made in a darkened respirometer (Fig.…”

“…The standard metric for the precision of temperature regulation is the slope of the regression line relating T th with T a (e.g. Chown and Scholtz, 1993;Merrick and Smith, 2004;Morgan, 1987;Oertli, 1989;Stone and Willmer, 1989;Verdu et al, 2004;Verdu et al, 2006). While a simplistic regression approach such as this ignores much of the detail regarding an insect's thermoregulatory ability (Chown and Nicholson, 2004), it nevertheless provides a coarse index of thermoregulatory precision under the conditions of measurement.…”

“…The slopes are quite variable in other beetles that are measured as they fly into light traps or in experimental enclosures. They range from essentially zero to 0.64 in several species (Chown and Scholtz, 1993;Merrick and Smith, 2004;Morgan, 1987;Oertli, 1989;Verdu et al, 2004;Verdu et al, 2006). This variation shows that the slope of the temperature relationship provides limited information about the factors influencing thermoregulatory precision, because the slope is affected by the balance between heat production and heat loss, both of which are independently variable.…”

“…Data for respiration and body temperature make it possible to estimate thermal conductance of the beetles without having to heat a dead insect artificially and calculate from a cooling curve in still air (Casey and Joos, 1983;Chown and Scholtz, 1993;Merrick and Smith, 2004;Morgan, 1987). The slope of the curve in Fig.…”

“…Scarab fig beetles, Cotinus texana, show T th in the region of 30-40°C during flight at T a down to 20°C (Chappell, 1984). There are other examples of high body temperatures of flying beetles (Bartholomew and Casey, 1977a;Heinrich and McClain, 1986;Merrick and Smith, 2004;Oertli, 1989;Verdu et al, 2004;Verdu et al, 2006).…”